Closure devices for tank filler necks in motor vehicles designed as screw-on caps, i.e., lockable screw-on caps, are known in the art. Normally, the tank filler neck and the screw-on cap are concealed behind a tank flap that continues the contour of the vehicle body and as a rule is painted the same color as the car.
Opening the tank filler neck is sometimes uncomfortable, especially in motor vehicles with diesel engines, because fuel residues together with dust collects on the screw-on cap, which causes the vehicle user to get soiled.